Extended Reach Drilling Research Articles

Reducing Torque and Drag in Extended-Reach Wells Using Thermoplastic Polymers for Protective Sliding Rings

Extended-reach drilling represents an advanced way of drilling and accessing reservoirs that were previously economically not feasible to drain, impossible to reach or in an environmentally sensitive area. One of the main issues that appears while drilling such wells is caused by the high values of friction factor which cause high values of torque and drag. One of the suggested solutions is to use a protective sliding ring made from materials such as POM, Teflon and PA6 in combination with lubricants added to a polymer mud system. First, measurements were conducted on a lubricity tester to choose the best material and, after finishing, a mechanical wear test was conducted on a specially designed device to measure mechanical wear. Results showed that Teflon showed lower values of friction factor in comparison to steel and the mechanical wear was minimal. The lowest value of friction force was recorded for blocks made from Teflon in tested mud systems. It is also noticeable that, in polymer mud with weighting additives and lubricant, the value of the friction force is higher than in polymer mud with lubricant only.

RESEARCH INNOVATIONS IN DIRECTIONAL AND HORIZONTAL DRILLING AND SIDETRACKING TECHNIQUES

Directional and horizontal drilling, and sidetracking techniques have become integral components of the oil and gas industry, which allows access to hydrocarbon reserves in challenging environments. This paper provides an overview of these drilling methods and explores recent trends in the development of technical equipment for horizontal drilling and sidetracking. Directional drilling allows for drilling at various angles, including horizontal and multilateral, providing access to reservoirs beneath the Earth's surface. This technique involves specialized equipment and precise control of the drill bit's direction and deviation, resulting in better reservoir management, increased productivity and reduced environmental effect. Horizontal drilling, on the other hand, involves drilling laterally through subsurface rock formations, particularly beneficial for accessing unconventional reservoirs (shale formations). Horizontal drilling allows operators to access more of the formation, resulting in increased productivity and reduced environmental footprint. Sidetracking techniques are employed to redirect the path of a wellbore, necessary for avoiding geological hazards, accessing untapped reservoirs, or bypassing damaged sections of the well. This process requires careful planning, specialized equipment, and skilled personnel to ensure successful execution while minimizing risks. The paper also discusses modern trends in the development of technical equipment for horizontal drilling and sidetracking technology. These include automation and robotics to improve drilling efficiency and safety, advancements in drilling fluids and measurement-while-drilling (MWD) technologies for better wellbore stability and real-time data acquisition, and innovations in extended reach drilling (ERD) tools and casing and cementing solutions. Additionally, there is ongoing development in sidetracking techniques to improve efficiency and reliability, such as whipstock and casing exit technologies. The Ultrashort-Radius Radial System (URRS) is highlighted as an advanced drilling technology, enabling access to reservoirs with restricted space or challenging geometries. Although challenges such as cost and adaptation to downhole conditions remain, ongoing research and development is aimed at overcoming these barriers and demonstrating the feasibility of innovative drilling technologies. Ultimately, these advances contribute to the industry's goal of maximizing hydrocarbon production while ensuring operational efficiency and environmental sustainability. Keywords: directional drilling, horizontal drilling, sidetracking techniques, technical equipment development, ultrashort-radius radial system, laser drilling.

Study on flow pattern transition of cuttings transport in extended-reach drilling

Inadequate hole cleaning is one of the major challenges in extended-reach drilling, especially prominent in large-sized hole sections, such as 121/4-in. section. As the drilling parameters including flow rate, ROP and rotational speed change, the cuttings flow pattern converts between fully suspended flow, two-layer flow, and three-layer flow. However, most existing cuttings transport models only study the problem of cuttings transport under a certain flow pattern and do not consider the dynamic conversion of different cuttings flow patterns. Pipe rotation plays a key role in cuttings transport in rotary drilling, but the existing studies have not fully revealed the effect of pipe rotation on the conversion of cuttings transport patterns. In this paper, a stirring diffusion factor is presented to quantify the effect of pipe rotation on cuttings transport, and the mathematical expression of the stirring diffusion factor is obtained through numerical simulations and the nonlinear regression method. Secondly, the critical conditions for the conversion of cuttings flow patterns are obtained by combining mechanical analysis and numerical simulation results, clarifying the applicable scope of different cuttings flow patterns. According to the comparison with experimental results, the prediction error of the new model considering the conversion of cuttings flow patterns is not higher than 11.1%, and the minimum prediction error is only 3.07%. Thirdly, the flow pattern maps for cuttings transport under different drilling parameters are drawn to provide guidance for the identification of cuttings transport pattern and optimization of drilling parameters. Finally, the flow pattern maps are applied to a case study of an extended-reach drilling. The results show that there is a delay effect in the conversion of cuttings flow patterns due to the nonlinear characteristics of annular geometry. Furthermore, the effects of flow rate, ROP and rotational speed on cuttings transport patterns are not independent, but mutually reinforcing and constraining each other. Inappropriate selection of drilling parameters will result in three-layer flow of cuttings transport, and then pipe sticking is likely to occur. The cuttings transport pattern can be converted from three-layer flow to two-layer flow by optimizing drilling parameters, which can significantly improve the hole cleaning effect.

Hole cleaning evaluation and installation spacing optimization of cuttings bed remover in extended-reach drilling

In extended-reach or long-horizontal drilling, cuttings usually deposit at the bottom of the annulus. Once cuttings accumulate to a certain thickness, complex problems such as excessive torque and drag, tubing buckling, and pipe stuck probably occur, which results in a lot of non-productive time and remedial operations. Cuttings bed remover can efficiently destroy deposited cuttings in time through hydraulic and mechanical stirring effects. This paper aims to build a method for hole cleaning evaluation and installation spacing optimization of cuttings bed remover to improve the wellbore cleaning effect. Firstly, a Computational Fluid Dynamics approach with Eulerian–Eulerian multiphase model was utilized to investigate the mechanism of cuttings transportation, and a new type of cuttings bed remover was designed. Next, an evaluation method of hole cleaning effect of remover was established. After that, the effects of several drilling parameters on hole cleaning including flow rate of drilling fluid, rotational speed of drillpipe, rate of penetration, wellbore size, rheological property of drilling fluid, and remover eccentricity on the performance of cuttings bed remover were investigated. The results demonstrate that the new type of remover with streamline blade performs better than conventional removers. The efficiency of hole cleaning is greatly improved by increasing the rotational speed of drillpipe, flow rate of drilling fluid, remover eccentricity, and 6 rpm Fann dial reading for drilling fluid. While higher rate of penetration and large wellbore size result in worse hole cleaning. These findings can serve as an important guide for the structure optimization design of cuttings bed remover and installation spacing of removers.

Interaction between Pipe Rotation and Cuttings Transport in Extended-Reach Drilling: Mechanism, Model, and Applications

Summary High drag and torque on drillstring and difficulty in hole cleaning are two major challenges in extended-reach drilling, and these two challenges are usually coupled with each other. However, previous studies considered the drillstring mechanics and hole cleaning as two relatively independent issues and studied them separately, which cannot fully reveal the complex mechanisms of pipe sticking and obtain proper drilling parameters to ensure hole cleaning and reduce drag and torque. To solve this problem, in this paper we present the concept of pipe-cuttings interaction and elaborate on the two interaction mechanisms, which are the effect of pipe rotation on cuttings transport and the effect of cuttings distribution on pipe load. Second, we introduce the stirring diffusion factor and pipe-cuttings contact stress to quantify the pipe-cuttings interaction, and we obtain their mathematical expressions through nonlinear regression of numerical simulation results. Third, we establish the mechanical pipe-cuttings interaction model by modifying and combining the tubular mechanical model and the cuttings transport model. Finally, we validate the interaction model and apply it to a case study of extended-reach drilling in the South China Sea. The results show that the interaction model is of high prediction accuracy and is superior to the conventional tubular mechanical and cuttings transport models because the interaction between pipe rotation and cuttings transport is sufficiently considered. The problem of poor hole cleaning for a 12¼-in. section is serious, and pipe sticking occurs frequently for the extended-reach well in the case study because the stationary bed height is more than 10% in actual drilling. It is usually difficult to ensure hole cleaning of a 12¼-in. section by only optimizing a single parameter of rate of penetration (ROP), flow rate, or rotational speed, but optimizing two of the parameters at the same time can achieve better results. Lastly, we establish a recommended chart of drilling parameters, which can aid engineers in making comprehensive recommendations on drilling parameters.

A New Model for Cleaning Small Cuttings in Extended-Reach Drilling Based on Dimensional Analysis

A wellbore’s cleanliness affects drilling efficiency, economy and drilling safety directly in extended-reach drilling operations. Wellbore cleaning in extended-reach drilling has always been a tough problem. Field experience has shown that inefficient transport of small cuttings is a main factor for excessive drag and torque during extended-reach drilling. However, very little is known about the transport of small cuttings. In this paper, we use the data fitting method of dimensional analysis and regression analysis to establish a wellbore cleaning model for high-inclination sections, then use water and Polyanionic Cellulose (PAC) as a drilling fluid to analyze the settlement cleaning of small cuttings in the wellbore. The data from the example wells were used for field simulations to finally derive many factors like drilling fluid density, drilling fluid displacement, drill pipe rotation speed, diameter of cuttings and annulus hydraulic diameter, which affect the thickness of the dimensionless cutting bed. The results show that the dimensionless cutting thickness decreases with increasing drilling fluid density, drilling fluid displacement and drill pipe rotation speed; and increases with increasing cutting size and annular hydraulics diameter. Meanwhile, the effect of drilling fluid discharge, drill pipe rotation speed and cutting size on the thickness of the dimensionless cutting bed decreases as their values increase. This model can be utilized to design parameters in drilling and to predict the transport of cuttings in high-inclination sections. The successful establishment of the wellbore cleaning model for small cuttings in high-inclination sections of extended-reach drilling wells is highly innovative, which is a successful combination of theory and practice and has important guiding significance for promoting the development of wellbore cleaning technology.

Selection of Optimal Well Trajectory Using Multi-Objective Genetic Algorithm and TOPSIS Method

This study presents a novel approach for optimizing well paths in extended reach drilling (ERD) wells. Different trajectories can be used for ERD wells, each with its pros and cons. Previous research overlooked certain objective functions in single-objective optimization and lacked an autonomous method for selecting the best solution from Pareto optimal solutions in multi-objective optimizations. Furthermore, they lacked comparing different profiles in well design. Risk assessment and operational factors, which greatly influence optimization and drilling success, were insufficiently considered. This study utilized the multi-objective genetic algorithm (MOGA) and the technique for order preference by similarity to an ideal solution (TOPSIS) method to select the optimal well path based on torque, wellbore length, risk (e.g., keyseat), and required tools. First, all possible trajectories were determined, and MOGA identified the optimal path with minimal torque and length. The fuzzy decision-making method automatically selected the best solution from the Pareto optimal solution set. The associated risks and required tools are evaluated for each trajectory. Finally, the TOPSIS method selected the optimal trajectory based on torque, length, risks, and required tools. The case study demonstrated that the undersection path was the most advantageous trajectory for ERD wells, with a 60% closeness to the ideal state. The multiple build trajectory achieved 57% closeness, while the build and hold and double build paths had lower closeness values (43 and 28%, respectively). Consequently, it can be inferred that in the context of ERD wells, it is preferable to carry out the deviation process at deeper depths.

Cuttings transport: Back reaming analysis based on a coupled layering-sliding mesh method via CFD

Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling. The mechanism of cuttings transport under the back reaming operation, which is frequently adopted to remove the cuttings, has been investigated in this study. To this end, a coupled layering-sliding mesh method with the Eulerian-Granular approach has been established innovatively. The dynamic layering method has been employed to simulate the axial motion of the pipe, whereas the sliding mesh method has been used to simulate the pipe rotation. The back reaming operation of a connector-furnished pipe has been simulated, and the sensitive parameter analysis has been conducted. The results thus obtained demonstrate that the increase in the initial bed height, inclination, and the diameter and length of the connector causes a significant increase in the cuttings concentration. In addition, the cuttings concentration is observed to decrease significantly with the pipe rotation speed. Furthermore, two main factors contribute towards the cuttings accumulation around the connector, namely, the difference in the cross-sectional area and the pushing effect of the connector—like a “bulldozer”. The “bulldozer” effect of the connector dominates when the tripping velocity is significant compared to the velocity of the cuttings. Conversely, the effect of the difference in the cross-sectional area becomes the leading factor for cuttings accumulation. The “bulldozer” effect of the connector causes a more severe impact on hole cleaning. In both cases, increasing the tripping velocity only mildly affects the cuttings concentration. It is therefore suggested that the tripping velocity should be slower than that of the sand during the back reaming operation. Furthermore, increased fluid velocity might lead to a higher accumulated cuttings concentration around the connector when the cuttings bed has not entirely passed through the connector. A significant flow rate can be safely applied after the cuttings have passed through the connector furnished with a large diameter, such as the bottom hole assembly. This exploration serves as an essential guide to predicting and controlling tight spots while back reaming.

CNPC, Sinopec Drill Ultra Deep in Search of Energy Security

_ China has spudded the country’s first ultradeep scientific exploration well exceeding 10,000-m depth as drilling began 30 May on CNPC’s Take-1 borehole in the Fuman oil field which is situated in the Taklamakan Desert of the Xinjiang Uygur autonomous region. CNPC (China National Petroleum Corp.) operates Fuman, which produced a third of Xinjiang’s Tarim Basin oil output in 2022, and aims to drill to a design depth of 11,100 m in record time using its own automated drilling rig equipped to cope with the extreme temperatures and pressures found in Northwest China, China state media reported. In its current Five-Year Plan, China aims to develop Fuman into a field capable of producing 35.7 million BOE annually by 2025. Fuman is the country’s largest ultradeep field and Tarim’s main crude oil production block, with reserves believed to exceed 71.5 billion bbl, according to CNPC. Journey to the Center of the Earth It took the Soviet Union 20 years to drill what is so far the world’s deepest well—the Kola Superdeep Borehole—which Russia sealed off and abandoned in 1992 after having reached a depth of 12,262 m (7.5 miles). There, drillers encountered 180°C (356°F) which deformed drill bits and pipes and made rocks so malleable they resembled plastic. CNPC expects its new automated, 82-m-high, 2,000-ton rig to penetrate 11,100 m of over 10 layers of continental strata in a record 457 days, reaching rock from the Cretaceous period that formed 66 million to 145 million years ago. China may be right to call its new drilling machine “the world’s first” automated rig capable of reaching 12,000 m considering details of its functionality. NOV built the Doyon 26, nicknamed “The Beast,” for Doyon Drilling to deploy on Alaska’s North Slope (Alpine field) under a long-term contract with ConocoPhillips, according to Tony Crawford, who worked nearly 2 decades in drilling and business development for Nabors in Alaska, Russia, and Kazakhstan, and in rig manufacturing for NOV in Russia and the US. With the help of the “The Beast,” Alpine was the first North Slope field developed exclusively with horizontal well technology, accessing 50 square miles of subsurface from a single drilling pad, according to ConocoPhillips. “It looks like the Chinese have created their ‘beast,’ have automated it, and added high-pressure and high-heat equipment,” said Crawford, who now owns Inerfuel, a Houston company that promotes nanO2 combustion catalyst to reduce carbon emissions in drilling. NOV’s “The Beast” is designed for extended-reach drilling and can reach a depth of 12,192 m, but with a drilling crew on board, he said. “Nabors has a robotic rig that is fully automated, called PACE-R801, but its maximum drilling depth is about 6,500 m. Drillmec has automated control systems, but not automated pipe handling and (other) equipment. “All the wells (where Doyon 26) is drilling are low to medium pressure, 5,000 psi or less, low to medium heat (50–80°C); nothing like China,” Crawford said of the North Slope. “The formations there are super soft; imagine drilling in clay mixed with sand.”

Optimized Engineering and Drilling Practices Help Break Record for Extended-Reach Well

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 204550, “Breaking ERD Records With Optimized Engineering and Practices: Making the Impossible Possible,” by Hussien Alzaki, SPE, Saudi Aramco; Nadhir Rahmani, Schlumberger; and Matthew Carr, K&M Technology Group. The paper has not been peer reviewed. _ The complete paper describes preplanning, execution, and results of extended-reach drilling (ERD) with a large-bore design of 12¼ in. as the main stepout section and deploying 9⅝-in. casing on a shallow true vertical depth (TVD) of 4,200 ft. Progressive increase of ERD ratio and complexity from one well to the next was planned and executed until a record-breaking well had been achieved, deploying 8 km of 9⅝-in. casing with a 5.4 ERD ratio at 26,179 ft total depth (TD) horizontally all the way. Planning Consideration and Risk Assessment The presented ERD campaign was unusual because of its combined ERD ratio and very shallow TVD for the long horizontal sections. In addition to the obligation to reach the targeted formation in a 12¼-in. hole, complex challenges were addressed, such as the obligation to kick off and drill large holes (12¼-in. horizontal hole section and 9⅝-in. casing) up to a 5.4:1 ERD ratio at 4,200 ft (approximately 1,300 m) TVD. The solution involved implementation of technically modeled engineered solutions that were verified during execution. Operational procedures included the following: - Proper planning and execution of well profiles to ensure optimal placement in a specific formation and minimum side force - Drilling and tripping procedures to ensure the lowest friction factor (FF) and allow drilling to TD with a limited rig capability - Engineered solutions for casing-running technologies, which involved rotation and conventional running and flotation Following risk assessment and the multiple peer reviews made for the subject well, a drilling plan was established that addressed the anticipated main limitations, which included the following: - Bottomhole assembly (BHA) and drillstring design to allow reaching TD within optimal rig capacities - Bit selection to reduce the number of - runs needed to two (three maximum if a contingency were to be considered) - Total dissolved solids (TDS) torque-limit management (30,000 lbf-ft at 180 rev/min) - A rig-pumping pressure limit of 4,600 psi - Hole-cleaning and FF management to prepare for deployment of 9⅝-in. casing

Technology Focus: Extended-Reach and Complex Wells (May 2023)

A clear change in the last 2–3 years is that the energy transition is becoming the undisputable trend for almost all major oil and gas companies and oilfield services providers, as evident from the news of rebranding, the roll-out of companies’ new strategies, and announcements of commitments to net zero. Geothermal energy, especially within deep, hot, dry rock, is abundant around the globe. It can be a great opportunity for the majors to boost their energy-transition process and open new business opportunities. Previously, however, deep geothermal development activities were rather limited and participation from the majors was sporadic. One reason was that drilling into such extra-hot and extra-deep impermeable rock could render excessively high cost and risk, making the development of deep geothermal energy far from economical and scalable and discouraging many companies from entering this hot spot. The domain expertise and technologies in the oil and gas industry such as integrated project planning and operating, extended-reach drilling (ERD), high-pressure/high-temperature drilling tools, multilateral drilling and completions, geomechanics, flow and thermal dynamics modeling, and artificial intelligence have been fueling the ongoing march for new records on ERD, multilateral, and other complex wells. They have made it possible to drill faster, further, and with more production, which will be the keys to accelerating the learning curve, filling the technology gap, and breaking the economic barrier on deep geothermal drilling, which in turn will attract more players to this new arena. A bold move of the majors into deep geothermal drilling could accelerate the removal of the economic and technical hurdles in harnessing the enormous baseload renewable energy and meanwhile backfeed new drilling technologies developed in deep geothermal applications to the oil and gas industry for a more sustainable future. Recommended additional reading at OnePetro: www.onepetro.org. SPE 206616 Deep Geothermal Well-Construction Problems and Possible Solutions by Mikhail Yakovlevich Gelfgat, Gubkin University, et al. SPE 200792 Lessons Learned and Case Studies of Overcoming Sustained Casing Pressure in Extended-Reach Wells by Svetlana Nafikova, SLB, et al. IPTC 21439 Application of Multilateral Wells for Production and Enhanced Oil Recovery: Case Studies From Canada by Eric Delamaide, IFP-Technologies

Expertise in Complex-Well Construction Leveraged for Geothermal Wells

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 204097, “Constructing Deep Closed-Loop Geothermal Wells for Globally Scalable Energy Production by Leveraging Oil and Gas Extended-Reach Drilling and High-Pressure/High-Temperature Well-Construction Expertise,” by Eric van Oort, SPE, Dongmei Chen, SPE, and Pradeepkumar Ashok, SPE, The University of Texas at Austin, et al. The paper has not been peer reviewed. _ In the complete paper, deep closed-loop geothermal systems (DCLGS) are introduced as an alternative to traditional enhanced geothermal systems (EGS) for green energy production that is globally scalable and dispatchable. The authors demonstrate that DCLGS wells can generate power on a scale comparable to that of EGS. They also highlight technology gaps and needs that still exist for economically drilling DCLGS wells, writing that it is possible to extend oil and gas technology, expertise, and experience in extended-reach drilling (ERD) and high-pressure/high-temperature (HP/HT) drilling to construct complex DCLGS wells. Introduction CLGS is considered a subset of EGS, but the authors write that it is a distinct entity. EGS mostly involves well designs that rely on fractures for heat extraction. Such systems are different from CLGS wells in that the latter use closed conduits for thermal fluid circulation and heating. CLGS relies on fluids pumped through a closed loop. The authors treat CLGS systems as being different from EGS systems, with the understanding that drilling technologies discussed in the paper as enablers for CLGS wells apply equally to EGS wells. In the geothermal (GT) domain, the majority of attention and funding currently is assigned to EGS projects. A case is made in the complete paper to continue to develop DCLGS technology because of its favorable risk profile compared with EGS. Part I of the complete paper introduces a hydraulic model coupled with a thermal model suitable for calculating the power generation of DCLGS wells. This synopsis concentrates instead on Part II of the complete paper, in which technology gaps and needs of DCLGS drilling and well construction are highlighted and opportunities identified where oil and gas experience and technology can be directly applied and leveraged. Similarities and Differences of Deep GT and Oil and Gas HP/HT Wells - GT wells generally use larger production hole sizes than typical land wells. - Casing-cement annuli typically are cemented back to surface. - GT wells can be drilled in more-forgiving pore-pressure fracture gradient (PPFG) environments with wider drilling margins than geopressured HP/HT wells in hydrocarbon systems. - Severe lost circulation appears to be a universal problem in deep GT wells. - Drilling costs can account for 50% or more of the total capital costs for a GT energy project. - Data sets on GT wells are much smaller than those for oil and gas wells.

Extended-Reach Drilling (ERD)—The Main Problems and Current Achievements

With the development of different segments within the drilling technology in the last three decades, well drilling has become possible in harsh downhole conditions. The vertical well provides access to oil and gas reserves located at a certain depth directly below the wellsite, and a large number of vertical wells are required for the exploitation of hydrocarbons from spatially expanded deposits. However, the borehole can deviate from the vertical well, which means that the target zone can be reached by a horizontal directional well. With this type of well, especially in the case of drilling an extended-reach well (ERW), the length of the wellbore in contact with the reservoir and/or several separate reservoirs is significantly increased, therefore, it is a much better option for the later production phase. Unfortunately, the application of extended-reach drilling (ERD technology), with all of its advantages, can cause different drilling problems mostly related to the increased torque, drag, hole cleaning and equivalent circulation density (ECD), as well as to an increase in the well price. Overcoming these problems requires continuous operational change to enable operators to address downhole challenges. Today, the longest well reaches 15,240 m (50,000 ft), which raises the question of the technological and economic feasibility of this type of drilling project, especially with the lower oil price on the energy market. This paper provides a comprehensive overview of extended-reach drilling technology, discusses the main problems and analyzes current achievements.

Research on dynamic prediction of tubular extension limit and operation risk in extended-reach drilling

Extended-reach wells have been widely applied to efficient development of oil and gas resources in complex areas such as oceans, beaches, lakes and mountains. Extended-reach drilling has the characteristics of many constraints, high implementation difficulty and high operation risk, and the accurate prediction of tubular extension limits and operation risks is very significant for safe drilling. Firstly, local tubular deflection curves and additional contact forces due to discontinuity effects are firstly deduced, and an amended torque & drag model of tubular strings is built. Secondly, a dynamic inversion method of friction factors was presented by introducing the weight function related to well depth and considering the difference of friction factors on cased and open-hole sections. Next, a dynamic prediction of tubular extension limit and operation risk is built by combining the amended tubular mechanical model, inversion model of friction factors. At last, the above theoretical models are applied to a case study. The results indicate that curvature discontinuity and stiffness discontinuity increase contact forces obviously in build-up and azimuth turning sections, which further increase friction force and torque a lot. The long-term, short-term and real-time tubular extension limits and operation risks can be obtained by setting different values of p.

Concurrent 5. Presentation for: Seamless in seam – new geosteering technology delivered challenging coal seam gas project with success

Presented on Tuesday 17 May: Session 5 A recent coal seam gas (CSG) appraisal project posed several challenges. The target reserve area had limited seismic data available and yet had complex structure with several faults of variable orientations and throws between 2 and 25 m. Dual-lateral extended-reach drilling (ERD) wells needed to be drilled in order to access this reserve, with a 1000 m in-seam section for each lateral planned to maximise production. Conventional technologies for CSG projects included motor bottom hole assembly with a boundary mapping tool for geosteering in the coal seams. However, for drilling ERD wells in this unknown area, these methods were insufficient to deliver success, due to the limited mapping capabilities and drilling efficiencies. Recently there has been significant development on the directional resistivity-based mapping tool, on both the measurements and processing. The operator adopted a new mapping-while-drilling technology which has the first-in-industry tool with axial, tilted and transverse antennas integrated in one module. This new technology can provide high-resolution multilayer mapping with doubled depth of investigation, even when drilling out of the coal seam. The results from utilising this new tool, together with a rotary steerable system for directional control, were very encouraging. The new multilayer mapping-while-drilling tool mapped both the top and base of the coal seam throughout horizontal sections in-seam. In addition, it detected the coal seams during landing and after fault-crossing from up to 4 m true vertical depth away, enabling the team to navigate through complex fault zones confidently, and to deliver the project with success. To access the presentation click the link on the right. To read the full paper click here

Analysis of drilling difficulty of extended-reach wells based on drilling limit theory

With the continuous increase in vertical depths and horizontal displacements of directional wells, the difficulties of drilling operations continue to increase, and more accurate methods of drilling difficulty evaluation are needed. In this paper, a drilling difficulty evaluation method is built by combining drilling limit model and expert evaluation. Firstly, the concept of drilling difficulty index is introduced, and the method to calculate drilling difficulty index is established. Next, the meanings of five drilling difficulty levels are explained and the optimization design method with drilling difficulty as the target is built. At last, the theoretical model is applied to the extended-reach drilling of the Liuhua oilfield in the South China Sea, in which drilling difficulties are evaluated and the relationship between drilling difficulty and development control radius is revealed. The results indicate that extended-reach drilling in the Liuhua oilfield is on the “normal” difficulty level on average, rotary drilling in 8 1 / 2 -in. section is the most difficult, and the main constraint conditions are excessive torque and high friction. Through technology upgradation, the drilling difficulties are decreased, the development control radius increases from 6.6 to 11.4 km, and the maximum horizontal-to-vertical ratio increases from 5.3 to 8.7. Then, the development wells in marginal oilfields and adjustment wells in old oilfields can be drilled on “normal” difficulty level. Therefore, technology upgradation, especially drilling rig upgradation, is the most important development direction for extended-reach drilling in the South China Sea.

Seamless in seam – new geosteering technology delivered challenging coal seam gas project with success

A recent coal seam gas (CSG) appraisal project posed several challenges. The target reserve area had limited seismic data available and yet had complex structure with several faults of variable orientations and throws between 2 and 25 m. Dual-lateral extended-reach drilling (ERD) wells needed to be drilled in order to access this reserve, with a 1000 m in-seam section for each lateral planned to maximise production. Conventional technologies for CSG projects included motor bottom hole assembly with a boundary mapping tool for geosteering in the coal seams. However, for drilling ERD wells in this unknown area, these methods were insufficient to deliver success, due to the limited mapping capabilities and drilling efficiencies. Recently there has been significant development on the directional resistivity-based mapping tool, on both the measurements and processing. The operator adopted a new mapping-while-drilling technology which has the first-in-industry tool with axial, tilted and transverse antennas integrated in one module. This new technology can provide high-resolution multilayer mapping with doubled depth of investigation, even when drilling out of the coal seam. The results from utilising this new tool, together with a rotary steerable system for directional control, were very encouraging. The new multilayer mapping-while-drilling tool mapped both the top and base of the coal seam throughout horizontal sections in-seam. In addition, it detected the coal seams during landing and after fault-crossing from up to 4 m true vertical depth away, enabling the team to navigate through complex fault zones confidently, and to deliver the project with success.

Technology Focus: Extended-Reach and Complex Wells (May 2022)

In the past several decades, technology continuously pushed the technical limit of extended-reach and complex wells, bringing records for lateral length, depth, and number of laterals. In the past few years, however, the design and operations of extended-reach and complex wells started to evolve under the volatile oil market pricing conditions and the stride of digital transformation. The technology front is shifting from marching toward longer and more-complex wells to smarter wells with better return on investment (ROI). Artificial intelligence (AI) and machine learning, which can effectively mine deep insight from a large amount of drilling operational data and synthetic forward modeling data, are starting to shape the design and operations of extended-reach and complex wells. AI and machine learning have been demonstrating their ability to provide early warning of stuck pipe, reveal root causes of drilling accidents, improve drilling design, optimize completion design, and find new ways to improve production performance. Rather than competing on going even farther, U-shape (or “horseshoe”) wells have been drilled to tap shale gas through leveraging state-of-the-art extended-reach drilling technology and stimulation technology to improve the economics of the development of unconventional reservoirs. Looking to the future, the march toward longer extended-reach wells and more-complex multilateral wells to access formidable reservoirs will continue. The great potential, however, lies in the application of state-of-the-art extended-reach and complex well technology to versatile oil and gas fields (both conventional and unconventional) for the purpose of further improving ROI of the project, and AI and machine learning will play a vital role in enabling a step change in design and operations. Recommended additional reading at OnePetro: www.onepetro.org. SPE 202046 Automated Geosteering While Drilling Using Machine Learning—Case Studies by Ivan Denisenko Denisenko, Rogii, et al.

An Innovative Method for Designing Smooth Catenary Well Trajectories in Extended-Reach Drilling

A catenary well trajectory is known for its reduced drag and torque during drilling. Modern deflection tools have made it possible to drill catenary well trajectories efficiently, thanks to tool’s capacity of dynamic build rate that creates wellbore profile of varying curvature. However a method to design well trajectory with smooth transition from the kick-out point to the catenary section to reduce “dog-leg” and thus friction is still lacking. This paper presents a 2D mathematical solution to fill the gap. The solution uses equations of closed-form rather than numerical computations. The complete well trajectory profile involves a vertical section, a transitional arc section, a catenary section, and a horizontal/slant section. A case study is presented to compare the friction forces on the drill string in a catenary trajectory profile and a conventional trajectory profile of arc type. The calculation procedure of catenary trajectory design was realized in an MS Excel spreadsheet with direct inputs, which provides an excellent flexibility to meet well trajectory design requirement. The presented mathematical model is an easy-to-use and reliable tool for designing catenary well trajectories in extended-reach wells to minimize wellbore friction and thus increase well depth.

Buoyancy Force on a Plain or Perforated Portion of a Pipe

Summary Torque and drag models have been used for several decades to calculate tension and torque profiles along drillstrings, casing strings, and liner strings. Buoyancy forces contribute to the loads acting on the pipe and affect its interaction with the borehole wall. Torque and drag calculations account for these localized effects, as well as the material internal forces, torques, and moments on each side of the contact. When the analysis is applied to a discrete length of pipe, the cross sections at each end do not contribute to the buoyancy forces because they are not in contact with the fluid, except where there is a change in diameter or at the end of the string of pipe. We argue that it is important to check that the models used for solid pipe torque and drag calculations remain valid for sand screens, in particular, the extent to which the buoyancy forces acting on a perforated tube might differ from those on a solid pipe. Because the buoyancy force is the result of the pressure gradient acting on the surface of the pipe, the presence of holes may also influence the buoyancy force. We propose that there are theoretical differences between local buoyancy forces acting on plain or perforated tubes. This paper describes how to calculate the local buoyancy force on a portion of a drillstem by the application of Gauss’ theorem and accounting for the necessary corrections arising from the cross sections not being exposed to the fluid. We built an experimental setup to verify that the tension inside a pipe subject to buoyancy behaves in accordance with the derived mathematical analysis. With complex well construction operations, for instance during extended-reach drilling or when drilling very shallow wells with high buildup rates, the slightest error in torques and drag calculations may end up jeopardizing the chances of success of the drilling operation. It is therefore important to check that the basis of design calculations remain valid in those contexts and that, for instance, sand screens or slotted liners may be run in hole safely after a successful drilling operation.